1. Technical Field
The present disclosure is directed to a mask set, and more particularly, to a mask set for in-situ synthesizing probes of a microarray, a method of fabricating the mask set, and a method of fabricating the microarray using the mask set.
2. Description of the Related Art
Advances in the genome project have revealed genome nucleotide sequences of various organisms. Accordingly, there is a growing interest in microarrays. Microarrays are widely used for gene expression profiling, genotyping, detection of mutations and polymorphisms, such as single nucleotide polymorphisms (SNPs), analysis of proteins and peptides, screening of potential medicine, development and production of new medicine, and the like.
A microarray includes a plurality of probes fixed to a substrate. The probes may be directly fixed to the substrate by spotting or in-situ synthesized using photolithography and then fixed to the substrate. In particular, in-situ synthesis using photolithography is recently drawing attention because it facilitates mass production of microarrays.
A plurality of masks are used for the in-situ synthesis of probes. Each mask includes light-transmitting regions and light-blocking regions. In addition, each mask is allocated any one of a plurality of, e.g., four, probe monomers. If there are four probe monomers, a maximum of four separate masks are required to complete a monomer layer of a probe. If a probe is composed of 25 monomer layers, a maximum of 100 separate masks would be required.
The light-transmitting regions of each mask respectively correspond to probe cells where monomers are to be synthesized. Therefore, the pattern of each mask varies according to the sequence of target probes that are to be synthesized in each probe cell. That is, while light-transmitting regions may occupy an average of, for example, 25% of an entire mask, their proportion in each mask may be far smaller than the average according to the probe sequence of each probe cell. In the extreme case, some masks may have light-transmitting regions which occupy less than 1% thereof. If a proportion of the light-transmitting regions in some masks is excessively small, it is challenging to perform precise patterning during mask fabrication. For example, since the light-transmitting regions are either partially open or closed, light-transmitting regions of a desired size and/or shape cannot be secured. This situation aggravates as microarrays become more integrated.